The first explosion occurred in the center of Tentena, a predominantly Christian town in Sulawesi province. Authorities say a second blast, 15 minutes later, targeted those who had been attracted by the first explosion.
There have been no claims of responsibility for the bombings.
Tentena is 60 kilometers south of the coastal town of Poso - an area known for frequent clashes between Muslims and Christians that have claimed more than 1,000 lives in the last five years.
Indonesia has the world's largest Muslim population, but the area on the island of Sulawesi where Saturday's explosions took place is about evenly divided between Muslims and Christians.
Some information for this report provided by AP and AFP.